Axial turbocompressor

ABSTRACT

An axial turbocompressor having an annular compressor passage which is arranged concentrically around a rotational axis, is delimited radially on the outside by a passage wall, and in which rotor blades, which may be assembled to form a ring, are arranged in a rotatably mounted manner around the rotational axis, is provided. The free-ending tips of the rotor blades lie opposite the passage wall in each case, forming a gap, and the passage wall, in the axial section of the tips, at least partially has a wall structuring and wherein a bleed opening of a bleed passage is provided in the passage wall for the tapping of medium flowing in the compressor passage. In order to enable an exceptionally efficient bleed of medium flowing in the compressor passage, the bleed opening is located in the wall structuring.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of European Patent Office applicationNo. 11169109.3 EP filed Jun. 8, 2011. All of the applications areincorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention refers to an axial turbocompressor having an annularcompressor passage which is arranged concentrically around a rotationalaxis, is delimited radially on the outside by a passage wall and inwhich rotor blades, which can be assembled to form a ring, are arrangedin a rotatably mounted manner around the rotational axis, wherein thefree-ending tips of the rotor blades lie opposite the passage wall ineach case, forming a gap, and the passage wall, in the axial section ofthe tips, has at least partially a wall structuring (also known ascasing treatment) and wherein a bleed opening of a bleed passage isprovided in the passage wall for the tapping of a medium flowing in thecompressor passage.

BACKGROUND OF INVENTION

The afore-described arrangement is known from GB 2 158 879 A, forexample. The casing treatment is provided on the casing-side passagewall above an upstream-disposed rotor blade row and the bleed point forthe tapped air is located at a rotor blade row which is disposeddownstream thereof. In the bleed passage, provision is made, moreover,for a valve in order to tap different volumes of compressor air independence upon the operating state. Both measures enable a degree ofcontrol of the operation of the compressor for high pressure ratioswithout undesirable compressor phenomena, such as surging or separationphenomena, resulting in the process. It is disadvantageous, however,that the aforesaid design has proved to be unsatisfactory for a partialload operation of a gas turbine.

SUMMARY OF INVENTION

The object of the invention is therefore the provision of an axialturbocompressor in which the operating range is further improved by amore efficient avoidance of undesirable compressor phenomena.

A further object of the invention is the provision of a gas turbine withan axial turbocompressor according to the invention which avoidsimpermissibly high emissions particularly during partial load operation.

The object forming the basis of the invention is achieved with an axialturbocompressor according to the features of the claims. Advantageousdevelopments and embodiments are disclosed in the dependent claims ineach case.

According to the invention it is intended to locate the bleed opening inthe wall structuring. Therefore, not only is the simultaneous use of acasing treatment and the tapping of compressor air inside an axialturbocompressor proposed, but the combination is also put into effectlocally, specifically in the region of a single rotor blade row of theaxial turbocompressor. A backing up of the compressed air and anaerodynamically unfavorably high pressure ratio, associated therewith,in the subsequent compressor stages can therefore be avoided, which inthe main avoids the occurrence of the undesirable compressor phenomena.As a result of the combination according to the invention, the surgelimit of the compressor stage in question can be adjusted in aparticularly simple manner and in dependence upon the operating state.This, when the axial turbocompressor is used in a stationary gasturbine, enables a particularly low partial-load operation without theemissions limits being exceeded in the process. When being used in a gasturbine, a correspondingly small air volume for the partial load can bedirected into the combustion chamber, specifically by the tapping ofcompressor air, as a result of which the CO emissions are minimized.Therefore, air is extracted from the compressor in a specific manner sothat no unwanted fluidic effects occur, as can happen in the case ofconventional blow-off valves. Moreover, the tapping of air which isprovided in the casing treatment also assists the effect of the wallstructuring itself so that the casing treatment can be formed in a morespace-saving manner than a casing treatment without bleed openingslocated therein.

According to a first advantageous development, the wall structuring isvariable in its extent and/or form and as a result the bleed opening canbe at least partially uncovered. This embodiment enables, in a simpleconstruction, three operating states of the axial turbocompressor inall:

The axial turbocompressor is operated without casing treatment andwithout bleed of compressor air, preferably at full load,

The axial turbocompressor is operated only with casing treatment, butalso without the tapping of compressor air, preferably at high partialload, and

The axial turbocompressor is operated with casing treatment withsimultaneous tapping of compressor air, preferably at low partial load.

Consequently, the casing treatment, which is adjustable in its extent orform, does not serve solely for adjusting the wall structuring but atthe same time also serves as an actuating element for engaging ordisengaging the bleed of compressor air. This also enables aparticularly space-saving construction.

The aforesaid embodiment can be realized in a particularly simple mannerwith regard to construction if the wall structuring is variable in itsextent and/or form by means of a movable insert and the bleed opening islocated in a sidewall of the recess which accommodates the insert. Theinsert can be formed as a plug which can be displaced along the recess.Depending upon the position of the plug, either the recess is completelyclosed (for the first operating state), the recess is only partiallyclosed with the bleed openings still closed (for the second operatingstate), or the recess and the bleed opening are open (for the thirdoperating state). In this respect, solely by displacement of the plugalong its recess, which accommodates it, switching back and forthbetween the three aforesaid operating states can be carried out in asimple and reliable manner.

The bleed passage can be expediently connected on the flow dischargeside to a blow-off air system and/or cooling-air system.

It is also expedient to arrange a plurality of bleed openings per rotorblade ring. In this case, the medium flowing in the compressorpassage—in most cases air—can be evenly bled off from this, as seen overthe circumference of the axial turbocompressor. A gas turbineparticularly advantageously has an axial turbocompressor of thepreviously described type of construction, according to the invention,as a result of which the gas turbine can be operated at low partial loadparticularly with low emissions.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, features and characteristics of the invention areexplained in more detail based on preferred exemplary embodiments in thedrawing. Expedient embodiments result from advantageous combinations offeatures of the depicted devices according to the invention. In thedrawing:

FIG. 1 shows a stationary gas turbine with an axial turbocompressor in alongitudinal partial section,

FIGS. 2, 3 show in each case a detail through the cross section of thecasing of the axial turbocompressor with a first embodiment of a casingtreatment,

FIG. 4 shows in a perspective view a detail of the casing of the axialturbocompressor with a casing treatment according to a secondembodiment,

FIG. 5 shows a third embodiment of the device according to the inventionin a perspective view, and

FIGS. 6, 7 show a fourth embodiment of the combination according to theinvention of casing treatment and bleed opening.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows a stationary gas turbine 10 in a longitudinal partialsection. Inside, the gas turbine 10 has a rotor 14 rotatably mountedaround a rotational axis 12 and which is also referred to as a turbinerotor assembly. An inlet duct 16, an axial turbocompressor 18, atoroidal annular combustion chamber 20 with a plurality of burners 22arranged rotationally symmetrically to each other, a turbine unit 24 andan exhaust gas duct 26 are arranged in series along the rotor 14.Instead of an annular combustion chamber, the gas turbine may also beequipped with silo combustion chambers or with tubular combustionchambers.

The axial turbocompressor 18 comprises an annularly designed compressorpassage 25 with compressor stages, consisting of rotor blade rings andstator blade rings, arranged in series therein in a cascadic manner. Therotor blades 27, which are arranged on the rotor 14, lie opposite anouter passage wall 42 of the compressor passage 25 by their free-endingblade airfoil tips 29. The compressor passage 25, via a compressor exitdiffuser 36, opens into a plenum 38. Inside the plenum, the annularcombustion chamber 20 is provided with its combustion space 28 whichcommunicates with an annular hot gas passage 30 of the turbine unit 24.According to the depicted exemplary embodiment, four turbine stages 32,connected in series, are arranged in the turbine unit 24. A generator ora driven machine (not shown in either case) is connected to the rotor14.

During operation of the gas turbine 10, the axial turbocompressor 18inducts ambient air 34, as medium to be compressed, through the inletduct 16 and compresses this air. The compressed air is directed throughthe compressor exit diffuser 36 into the plenum 38, from whence it flowsinto the burners 22. Via the burners 22, fuel also makes its way intothe combustion space 28. There, the fuel, with the addition of thecompressed air, is combusted to form a hot gas M. The hot gas M thenflows into the hot gas passage 30 where it expands, performing work onthe turbine blades of the turbine unit 24. The energy released in themeantime is absorbed by the rotor 14 and on the one hand is used fordriving the axial turbocompressor 18 and, on the other hand, for drivinga driven machine or electric generator.

During operation of the gas turbine 10, and therefore during operationof the axial turbocompressor 18, conditions and aerodynamic phenomenamay occur, however, which partially limit the operation. In order toavoid the occurrence of these conditions and phenomena, at least onewall structuring is provided in the passage wall 42. This wallstructuring is not shown in FIG. 1 for the sake of clarity. This wallstructuring is also known as so-called “casing treatment” and is formedfor example as circumferentially endlessly extending grooves or casinggrooves which are distributed over the circumference and extend in theaxial direction. The wall structuring is usually provided in an axialsection of the compressor passage 25, in which the free-ending tips ofrotor blades 27 lie opposite the passage wall 42 in each case, forming agap.

FIGS. 2 and 3 now show in detail in cross section a detail through thepassage wall 42 of the compressor passage 25 in the region of a wallstructuring 44. The wall structuring 44, according to this firstembodiment, comprises a plurality of recesses 46 extending radiallythrough the passage wall 42. A radially displaceable insert 48, which isT-shaped in cross section, is seated in each recess 46. Two passagesopen into the recess 46 at the side. These passages are formed as bleedpassages 50. The opening 52 of the bleed passages is located in the wallstructuring 44, i.e. in the sidewall 54 of the recess 46. With theinsert 48 pushed inwards, the recess 46, and at the same time the bleedopenings 52, are fully closed (not shown).

In a position of the insert 48 which is shown according to FIG. 2, therecess 46 is partially opened for activating the aerodynamicallyeffective wall structuring 44 by the insert 48 having been displacedoutwards from its closed position affecting the recess 46. In thedepicted position of the insert 48, the first opening 52 of the bleedpassage 50 is uncovered so that at the same time compressor air can bebled, i.e. tapped, from the compressor passage 25 via the recess 46.According to the position of the insert 48 shown in FIG. 3, both bleedopenings 52 of the bleed passages 50 are uncovered. In this respect, thewall structuring 44 is variable in its extent and/or form and as aresult the bleed opening 52 can be at least partially uncovered.

FIG. 4 shows a second embodiment of the device according to theinvention in a perspective view. According to the second embodiment,provision is now made in the surface of the passage wall 42 pointingtowards the compressor passage 25 for circumferentially endlesslyextending grooves 60 along which the tips of the rotor blades, which arenot shown, circumferentially move. A plurality of bleed passages 62which are distributed uniformly along the circumference, of which onlysome are schematically shown, open into a sidewall 61 of one of thegrooves 60. In the case of this embodiment, the valve system for openingand/or closing the bleed of compressor air, however, is not formed bymovable inserts but constructed as a downstream system. The bleedpassages 62 can naturally also be distributed in a non-uniform manner

According to a third embodiment, which is shown in FIG. 5, the wallstructuring 44 is designed as axially extending grooves 64 distributeduniformly over the circumference of the passage wall 42, which groovesare located in a circumferentially rotatable insert 45 which is locatedin a recess 47 which is arranged in the passage wall 42 and correspondsto the insert 45. The bleed openings 52 of the bleed passages 50 lie inthe base of the recess 47. By means of the webs 49 of the insert 45,which are arranged between the grooves 64, the openings 52 are eitherclosed, partially open, or fully open, depending upon the position ofthe insert 45.

FIGS. 6 and 7 show, in a partially perspective view in each case, afourth embodiment of an adjustable casing treatment with bleed openings52 arranged therein. FIG. 6 shows a passage wall 42 with acircumferentially endless groove 66 in which is located a radiallydisplaceable insert 68 for the opening and closing of the wallstructuring 44 and also of the bleed opening 52 which is arranged in thesidewall 70 of the groove. In FIG. 6, the bleed opening 52 is closed bymeans of the insert 68. According to FIG. 7, the bleed opening 52 isopen.

In all, with the present invention, an axial turbocompressor 18 or a gasturbine 10 is proposed, having an annular compressor passage 25 which isarranged concentrically around a rotational axis 12, is delimitedradially on the outside by a passage wall 42, and in which rotor blades27, which can be assembled to form a ring, are arranged in a rotatablymounted manner around the rotational axis 12. In this case, thefree-ending tips 29 of the rotor blades 27 lie opposite the passage wall42 in each case, forming a gap, wherein in the passage wall 42 itselfprovision is at least partially made in the axial section of the tips 29for a wall structuring 44. In order to further improve the operatingperformance of the axial turbocompressor 18, provision is made for ableed opening 52 of a bleed passage 50 for the tapping and dischargingof air flowing in the compressor passage 25, which bleed opening islocated in the wall structuring 44 according to the invention.

While specific embodiments have been described in detail, those withordinary skill in the art will appreciate that various modifications andalternative to those details could be developed in light of the overallteachings of the disclosure. Accordingly, the particular arrangementsdisclosed are meant to be illustrative only and not limiting as to thescope of the invention, which is to be given the full breadth of theappended claims, and any and all equivalents thereof.

1. An axial turbocompressor, comprising: an annular compressor passagewhich is arranged concentrically around a rotational axis, is delimitedradially on the outside by a passage wall, and in which a plurality ofrotor blades, which may be assembled to form a ring, are arranged in arotatably mounted manner around the rotational axis, wherein thefree-ending tips of the plurality of rotor blades lie opposite thepassage wall in each case, forming a gap, and the passage wall, in theaxial section of the free-ending tips, at least partially has a wallstructuring, wherein a bleed opening of a bleed passage is provided inthe passage wall for the tapping of medium flowing in the compressorpassage, and wherein the bleed opening is located in the wallstructuring.
 2. The axial turbocompressor as claimed in claim 1, whereinthe wall structuring is variable in its extent and form and as a resultthe bleed opening is at least partially uncovered.
 3. The axialturbocompressor as claimed in claim 1, wherein the wall structuring isvariable in its extent or form and as a result the bleed opening is atleast partially uncovered.
 4. The axial turbocompressor as claimed inclaim 2, wherein the wall structuring is variable in its extent and formby means of a movable insert and the bleed opening is located in asidewall of the recess which accommodates the insert.
 5. The axialturbocompressor as claimed in claim 3, wherein the wall structuring isvariable in its extent or form by means of a movable insert and thebleed opening is located in a sidewall of the recess which accommodatesthe insert.
 6. The axial turbocompressor as claimed in claim 1, whereinthe bleed passage is connected on the flow discharge side to a blow-offair system and/or cooling air system.
 7. The axial turbocompressor asclaimed in claim 1, wherein provision is made for a plurality of bleedopenings per rotor blade ring.
 8. A gas turbine, comprising: an axialturbocompressor as claimed in claim
 1. 9. The gas turbine as claimed inclaim 8, wherein the wall structuring is variable in its extent and formand as a result the bleed opening is at least partially uncovered. 10.The axial gas turbine as claimed in claim 8, wherein the wallstructuring is variable in its extent or form and as a result the bleedopening is at least partially uncovered.
 11. The axial gas turbine asclaimed in claim 9, wherein the wall structuring is variable in itsextent and form by means of a movable insert and the bleed opening islocated in a sidewall of the recess which accommodates the insert. 12.The axial gas turbine as claimed in claim 10, wherein the wallstructuring is variable in its extent or form by means of a movableinsert and the bleed opening is located in a sidewall of the recesswhich accommodates the insert.
 13. The axial gas turbine as claimed inclaim 8, wherein the bleed passage is connected on the flow dischargeside to a blow-off air system and/or cooling air system.
 14. The axialgas turbine as claimed in claim 8, wherein provision is made for aplurality of bleed openings per rotor blade ring.